Light college works for her faith, as they primarily fight chaos. A Shallyan Light wizard would just focus more on opposing nurgle. I'm also quite sure that Shallya doesn't oppose smiting demons of any flavor, either. Downside is that not a lot of Apprentices make it past the choirs, Eike could be one of them. And that the college itself isn't the best positioned for 'business'
Grey college would likely be Mathilde's favourite (she's biased, though), because it's the safest for the empire. Being one of the Lords of the Grey college (and potentially her future master), she gets some say in what Eike ends up doing in the long run, which she could leverage to keep Wilhemina somewhat happy. Downsides are that her upbringing might not be a good fit.
Celestial college has the best synergy on the Magic/Business axis, i.e. using magic to improve business. Downside: Mathilde doesn't like the way Azyr influences Celestials' thinking, which might lead to disagreements down the line. But would be interesting as well.
The Gold college reverses the Magic/Business axis, i.e. using Business to improve Magic. Culturally, the college encourages the accumulation of wealth (and gold), which could be good, or bad. Though I'm inclined to think that having the upbringing she has, Eike will quite likely stay on the side of the angels. Not to mention, the Lord Magister Grey wizard silent partner.
Jade might be interesting, as it Synergizes with her Shallyan faith, and understanding of growth seems to be intrinsic to the college. Life wizards are also among the colleges that reproduce, so Wilhemina's empire might survive multiple generations, if under the stewardship of the Jade college. Hypothetically, Panoramia could take her magister exam and take her as an apprentice, which would draw her out of the college's cult, and draw her into our orbit. But that's a longshot, for multiple reasons.
For the other three winds, I can't think of any positives, and i'm not just going to list the downsides.